Technical Field
The present invention relates to a system and an apparatus for monitoring areas, and in particular, to a system and an apparatus for monitoring areas which are previously set to be monitored using laser light.
Background Art
An area monitoring system that detects an intruder within an area to be monitored by scanning the area to be monitored with laser light at each predetermined scanning angle, and a monitoring apparatus used in such an area monitoring system are known (for example, refer to JP-A-2014-181993).
Such area monitoring systems and monitoring apparatuses are typically provided with a rotating mirror that is rotated by a motor. Laser light is radiated towards the area to be monitored at each predetermined scanning angle, by the rotating mirror. A distance to an object is measured based on the amount of time from when the laser light is radiated, until the radiated laser light is reflected by the object and the reflected light is received. Detection of an intruder is thereby performed at each scanning angle.
Here, in the case in which an intruder is detected through use of reflected light, should the area to be monitored be within a range of 30 meters in the current state, for example, the laser light is required to be radiated at an output power which enables the laser light to reach at least twice the range, that is, 60 meters. However, the reflected light is required to be received with a certain degree of intensity (referred to, hereafter, as a light reception amount) to ensure measurement accuracy. In addition, the laser light scatters when reflected by an object. When such issues are taken into consideration, the actual required output of the laser light is required to be set, not to enable a reach of about twice the range, but even greater. It is known that the energy of laser light attenuates in inverse proportion to the square of the distance. Therefore, here, the required output of the laser light increases in an accelerating manner as the area to be monitored widens.
However, even should there be a desire to widen the area to be monitored, in reality, the fact is that the output of the laser light cannot be easily increased, from the perspective of safety. For example, when the area to be monitored is set to a range of 100 meters, the required output of the laser light is approximately 11 times the output required for the range of 30 meters, described above. Therefore, the output of the laser light may exceed a range that is considered safe should the laser light directly enter the human eye, such as the range of Class 1 laser output prescribed by JIS C 6802.
In addition, in the case in which the reflected light is used, the laser light also reaches outside of the area to be monitored due to the configuration. Therefore, when the output of the laser light is increased, persons outside of the area to be monitored may be affected in addition to persons inside the area to the monitored.
Meanwhile, the need for monitoring over an even greater distance is rising. An area monitoring system and a monitoring apparatus that are capable of monitoring over an even greater distance, while ensuring safety, are desired.
It is thus desired to provide an area monitoring system and a monitoring apparatus that are capable of monitoring over an even greater distance, while ensuring safety.